1815 has 12 divisors (see below), whose sum is σ = 3192. Its totient is φ = 880.

The previous prime is 1811. The next prime is 1823. The reversal of 1815 is 5181.

1815 = 17^{2} + 18^{2} + ... + 21^{2}.

It is a happy number.

1815 is nontrivially palindromic in base 14 and base 16.

1815 is an esthetic number in base 13, because in such base its adjacent digits differ by 1.

It is not a de Polignac number, because 1815 - 2^{2} = 1811 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

1815 is an undulating number in base 14 and base 16.

It is a plaindrome in base 6.

It is a nialpdrome in base 13 and base 15.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 1794 and 1803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 160 + ... + 170.

It is an arithmetic number, because the mean of its divisors is an integer number (266).

1815 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1815 is a deficient number, since it is larger than the sum of its proper divisors (1377).

1815 is a wasteful number, since it uses less digits than its factorization.

1815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30 (or 19 counting only the distinct ones).

The product of its digits is 40, while the sum is 15.

The square root of 1815 is about 42.6028168083. The cubic root of 1815 is about 12.1981005732.

Adding to 1815 its sum of digits (15), we get a triangular number (1830 = T_{60}).

Multiplying 1815 by its sum of digits (15), we get a square (27225 = 165^{2}).

1815 divided by its sum of digits (15) gives a palindrome (121).

Adding to 1815 its reverse (5181), we get a palindrome (6996).

It can be divided in two parts, 18 and 15, that added together give a palindrome (33).

The spelling of 1815 in words is "one thousand, eight hundred fifteen".

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